Enhanced anti-corrosion property of Hf modified (Ni,Pt)Al coating in high-temperature salt fog: DFT calculations and experimental analysis

• Pt element in NiAl bulk exhibits chemical inertness to interstitial S, Cl and O. • Hf element promotes oxidation , sulfidation , and chlorination of NiAl phase. • Co, Ta, W, Hf reduce embrittlement of coating/oxide interface induced by S, Cl, H. • Hf-addition to (Ni,Pt)Al coating enhances its high-temperature corrosion resistance . • Pre-oxidation can fully utilize the positive effect of Hf on interfacial adhesion. The β-NiAl phase, as a major intermetallic compound for enhancing resistance to high-temperature oxidation of nickel-based superalloys, suffers from extremely severe corrosion in high-temperature salt fog. Based on the purpose of enhancing anti-corrosion property of NiAl-based coating, this paper uses first-principles calculations to investigate the thermodynamic formation energy, diffusion behavior, interfacial adhesion (β-NiAl/a-Al 2 O 3 ) of alloy elements (Co, Cr, Mo, Re, Ta, W, Pt, Hf) and Cl, S, H, O in NiAl phase. The results indicate that Pt exhibits significant chemical inertness towards Cl, S, H and O, but it has no contribution to the enhancement of interfacial adhesion. In contrast, Hf element can serve as a reinforcing element for enhancing interfacial tensile strength and the risk of promoting internal oxidation, sulfidation, and chlorination was observed. Consequently, a low-Hf-content (Ni,Pt)Al coating with better corrosion resistance was prepared, and further optimized by applying pre-oxidation treatment. The excellent high-temperature salt fog corrosion resistance of Hf-(Ni,Pt)Al coating was fully analyzed, and the corrosion mechanism was proposed.